1. Field of the Invention
The present invention relates to an improvement to heat pumps employed alternatively for heating and cooling. In the heating mode, refrigerant gas bypasses the evaporator coil when ambient temperatures are extremely low, below temperatures required for efficient heating operation. Supplementary heat is provided by an electric resistive element enveloped within a liquid bath. The refrigerant circuit passes through and absorbs supplementary heat from the liquid bath.
2. Description of the Prior Art
Employment of vapor compression heat transfer devices for both heating and cooling has become commonplace. As applied to space heating and cooling for residences and other occupied buildings and spaces, such devices are generally termed heat pumps. A heat pump typically includes a refrigerant circuit including a compressor and two heat exchangers.
The present invention is directed towards the heating and cooling of living spaces, and the discussion of the prior art will proceed with this in mind. Therefore, the term "heat pump" will be employed. It will further be assumed that heat is rejected to or drawn from ambient air. In theory, heating is merely a reversal of cooling, or air conditioning operation. However, practical experience has shown that firstly, there is a critical ambient temperature for all known commercially available heat pumps. Below this critical temperature, heat pumps cannot abstract sufficient heat from the atmosphere to satisfy heating requirements. Substitute or supplementary heat sources must be called into play to maintain occupied spaces at satisfactory temperatures.
A second problem is that in the heating mode, when certain ambient temperature and humidity conditions exist, the heat exchanger in communication with the atmosphere will suffer from deposition of ice on its external surfaces. This ice effectively insulates against heat transfer, and the heat pump becomes ineffective.
These problems are well known, and various strategies have been set forth to remedy the same. Supplementary heat is generally employed to heat the occupied space, as illustrated in the examples below. It has also been prior art practice, although not illustrated herein by prior art examples, that heat is applied to remove ice deposited upon heat exchangers.
Heat pumps and air conditioners, which refer to vapor compression devices which move heat only from within a building to the ambient, exist as unitary devices, or window units, or as split systems. In a typical split system, the compressor and one heat exchanger are furnished as one unit, which is set in place on a concrete slab outside the building being heated and cooled. The second heat exchanger, together with a powered fan for forcing air and a duct system for distributing conditioned air, is located within the building. The two heat exchangers are connected by power and control electrical lines, and conduits of a refrigerant circuit.
A window unit has practical limitations which do not necessarily arise in a split system. Both location of the window unit and the size of the window unit require independence from cumbersome external heating devices, and especially from combustion based heating devices. A window unit is intended to be portable, and the permanent utility connections which are generally required for fuel supply, combustion air supply, and the like interfere with the practicality of a window unit.
As the present invention provides improvement to generally well known heat pumps and allied devices, the following patents will generally illustrate the art.
U.S. Pat. No. 3,589,437, issued to Kunihiro Shoji et al. on Jun. 29, 1971, teaches a heat pump having an electric heating element disposed in-line within a refrigerant chamber or conduit. The present invention avoids direct exposure of a heating element with the refrigerant.
U.S. Pat. No. 3,563,304, issued to William L. McGrath on Feb. 16, 1971, describes a liquid receptacle buried in the ground proximate a building. A refrigerant circuit passes through water contained within the receptacle for transfer of energy. The liquid is heated by an electric resistive heater extending thereinto. In the present invention, the liquid is an intermediate heat transfer medium rather than a storage medium. As will be gleaned from the accompanying specification, it would not be feasible to employ a separate, buried liquid receptacle with the heat pump of the present invention.
U.S. Pat. No. 3,768,274, issued to James K. Fink on Oct. 30, 1973, shows bypassing a condensing coil to control the amount. of cooling of air forced through the evaporator coil. Another bypass for temperature control is seen in U.S. Pat. No. 5,211,023, issued to Takaaki Matsuura on May 18, 1993. Circulation of refrigerant through heat exchangers other than the condensing and evaporating coils is selectable. In the present invention, the condensing coil is not bypassed, and no additional air-to-refrigerant heat exchangers are employed.
The precise combination of components employed in the present invention is not shown in the prior art.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.